Present combustion methods of internal combustion engines, but in particular also combustion methods which are in development, which provide a high level of valve overlap for high internal residual gas rates and/or late or early closing of the intake valves, place increased demands on the accuracy of the valve operation. The combustion methods which are in development are used to reduce the fuel consumption of the internal combustion engine, for example, by dethrottling. Characteristic valve timings, such as, for example, intake valve closes or valve overlap, have significantly stronger influence in these combustion methods on the fresh air cylinder charge or the internal residual gas quantity than is the case in conventional combustion methods. Incorrect valve timings result, in particular in the case of a pressure-based charge detection, in a charge error, since the charge in this case is not measured via a sensor, for example, a hot-film air flow meter (HFM), but rather is calculated via a model. In addition to the intake manifold pressure, the valve timings are also entered in this model.
Errors in the valve timings result, on the one hand, due to mounting and manufacturing tolerances of the cam drive including phase shifter and encoder wheel, and also via installation and sensor tolerances of the camshaft position sensor and via the sensing of the crankshaft position. Furthermore, an influence due to chain or belt lengthening is added over the service life of the internal combustion engine.
Various approaches exist for the adaptation of the valve timings. However, the known methods share the feature that an adaptation is not carried out based on the actual charge. Thus, for example, it is assumed that the mounting and manufacturing tolerances of the camshafts are significantly less than the sensor installation tolerances. In this case, since with a new internal combustion engine, i.e., there is not yet any chain lengthening upon approach of a reference position (for example, stops of the phase shifter), an angle error may be learned as a difference between a setpoint angle and the actual angle. Depending on whether the assumptions taken with respect to individual tolerances are correct or not, an improvement of the tolerance situation may be achieved in this way.